Allow muting/unmuting audio through media track API

media/renderers/renderer_impl.cc

Index: media/renderers/renderer_impl.cc
diff --git a/media/renderers/renderer_impl.cc b/media/renderers/renderer_impl.cc
index 38f49d4b66099adbb753cd1cccf67e8d79524e2d..8b687b7901802127c1ebca4bd209c83a40be8a03 100644
--- a/media/renderers/renderer_impl.cc
+++ b/media/renderers/renderer_impl.cc
@@ -205,8 +205,16 @@ void RendererImpl::SetVolume(float volume) {
   DVLOG(1) << __FUNCTION__;
   DCHECK(task_runner_->BelongsToCurrentThread());
 
-  if (audio_renderer_)
-    audio_renderer_->SetVolume(volume);
+  audio_volume_ = volume;
+  if (!audio_renderer_)
+    return;
+
+  if (audio_stream_currently_disabled_) {
+    DVLOG(1) << "SetVolume ignored since audio stream is currently disabled.";
+    return;
+  }
+
+  audio_renderer_->SetVolume(volume);
 }
 
 base::TimeDelta RendererImpl::GetMediaTime() {
@@ -225,6 +233,52 @@ bool RendererImpl::HasVideo() {
   return video_renderer_ != NULL;
 }
 
+void RendererImpl::OnEnabledAudioStreamsChanged(
+    const std::vector<const DemuxerStream*>& enabledAudioStreams) {
+  DCHECK(task_runner_->BelongsToCurrentThread());
+  DemuxerStream* audio_stream =
+      demuxer_stream_provider_->GetStream(DemuxerStream::AUDIO);
+
+  bool audio_stream_enabled = false;
+  for (const DemuxerStream* demuxer_stream : enabledAudioStreams) {
+    DCHECK_EQ(demuxer_stream->type(), DemuxerStream::AUDIO);
+    if (demuxer_stream == audio_stream)
+      audio_stream_enabled = true;
+  }
+
+  // TODO(servolk,wolenetz): Need to find a way to completely disable audio
+  // (i.e. stop audio decoder and switch video to wall clock) when audio stream
+  // is disabled, but for now just set volume to 0. crbug.com/599709
+  if (audio_renderer_) {
+    if (audio_stream_enabled && audio_stream_currently_disabled_) {
+      DVLOG(3) << __FUNCTION__ << " enabled audio. SetVolume=" << audio_volume_;
+      audio_stream_currently_disabled_ = false;
+      audio_renderer_->SetVolume(audio_volume_);
+    } else if (!audio_stream_enabled) {
+      DVLOG(3) << __FUNCTION__ << " disabled audio. SetVolume=0";
+      DCHECK(!audio_stream_currently_disabled_);
+      audio_stream_currently_disabled_ = true;
+      audio_renderer_->SetVolume(0);
+    }
+  }
+}
+
+void RendererImpl::OnSelectedVideoStreamChanged(
+    const DemuxerStream* selectedVideoStream) {
+  DCHECK(task_runner_->BelongsToCurrentThread());
+  DemuxerStream* video_stream =
+      demuxer_stream_provider_->GetStream(DemuxerStream::VIDEO);
+  if (selectedVideoStream) {
+    DVLOG(3) << __FUNCTION__ << " selectedVideoStream=" << selectedVideoStream;
+    DCHECK_EQ(selectedVideoStream->type(), DemuxerStream::VIDEO);
+    CHECK_EQ(selectedVideoStream, video_stream);
+  } else {
+    DVLOG(3) << __FUNCTION__ << " selectedVideoStream=none";
+    // TODO(servolk,wolenetz): Need to find a way to stop video decoding and
+    // rendering when the video stream is deselected. crbug.com/599709
+  }
+}
+
 void RendererImpl::DisableUnderflowForTesting() {
   DVLOG(1) << __FUNCTION__;
   DCHECK(task_runner_->BelongsToCurrentThread());